The present invention relates to an audio signal recording and reproducing apparatus, and more particularly to an audio signal recording and reproducing apparatus using a hard disk as a data recording medium.
In the audio field, apparatuses which can handle audio signals as digital audio data have become widely used. As an apparatus which can freely edit digital audio data, there is an audio signal recording and reproducing apparatus which uses a hard disk to store the digital audio data.
Such an audio signal recording and reproducing apparatus comprises an A/D converter which converts analog signals into digital audio data, a D/A converter which converts digital audio data into analog signals, a digital signal processor (DSP) which processes the digital audio data, a hard disk on which the digital audio data is recorded, and a central processing unit (CPU) which controls the entire operation of the entire apparatus.
In the above-mentioned audio signal recording and reproducing apparatus, the digital audio data is treated as a file of data by processing the digital audio data in accordance with a control program having a typical disk operating system (DOS) function.
The digital audio data is recorded as a digital audio data (DAD) file in a predetermined area of the hard disk. A plurality of DAD files are recorded on the hard disk. Additionally, directory information and file allocation table (FAT) data are also recorded in predetermined areas of the hard disk, respectively.
The DAD file is recorded over a plurality of clusters formed on the hard disk. The directory information includes the file name of each DAD file and the first cluster number corresponding to the DAD file name. Additionally, FAT data includes chain data which indicates the recording order of the clusters of the hard disk which clusters constitute the DAD file.
In the audio signal recording and reproducing apparatus, when a recording operation for audio signals is performed, DAD file data, the directory information data, and the cluster chain data of the FAT, which data correspond to the recorded audio signals, are produced and recorded in the predetermined areas of the hard disk. Additionally, reproduction procedure file data is generated which is used when reproducing the recorded audio signals. The reproduction procedure file data includes the corresponding DAD file name, an offset data which indicates the offset from the head of the DAD file to the start position of the reproduction, and the length of data to be reproduced.
The reproduction of the recorded audio signals is subject to the following procedure under the control of the controlling unit in accordance with a control program having a DOS function. First, the DAD name, the offset and the data length to be reproduced are obtained from the reproduction procedure file. The first cluster number of the DAD file corresponding to the obtained DAD name is then read by referring to the directory information.
Digital audio data corresponding to the recorded audio signals is read out from a series of clusters consisting of the first cluster and the corresponding clusters indicated by the cluster chain data in the FAT.
The controlling unit sends to the DSP the digital audio data read out from the DAD file on the hard disk. The DSP performs a predetermined process on the digital audio data and sends the data to the D/A converter, and the D/A converter then convert the digital audio data into audio signals so as to reproduce the original audio signals.
The above-mentioned data processing method using a DOS function is simple and has an advantage in that the production of the software requires less labor and efforts. However, due to the fact that the processing speed of the typical DOS is low, there may be a problem in that the reproducing speed of the recorded audio signals is not sufficiently high for the audio signal recording and reproducing apparatus which requires fast data processing.
Particularly, in a case where the hard disk drive having a low data transfer rate or in the case where a CPU having a low processing speed is used for the controlling unit, there may be a problem in that the reproduced audio sound has interruptions. In order to eliminate those problems, a high speed hard disk or a high speed CPU is required for the conventional audio signal recording and reproducing apparatus, and accordingly there is a problem in that the audio signal recording and reproducing apparatus is expensive.